1 Field of the Invention
The present invention relates to a magnetic recording medium such as a magnetic tape and a magnetic disk. More particularly, the present invention relates to a magnetic recording medium for high-density recording which causes few dropouts and has excellent electromagnetic conversion characteristics and excellent running durability.
2. Description of the Related Art
A variety of magnetic recording media, such as magnetic tapes (e.g., a video tape) and magnetic disks for computer memories, have been in use. The demand for high performance of these magnetic recording media, particularly the demand for recording density and running durability has been increasing from year to year.
An increase of recording density is achieved by, for example, smoothing the surface of a magnetic recording medium or a magnetic head so as to reduce the spacing loss between the medium and the head. On the other hand, many proposals have been made to date on improvement of durability. For example, Japanese Patent Laid-Open No. 4-157616 proposes adding to a magnetic layer a combination of a relatively hard organic solid additive and a relatively soft organic solid additive.
It has been difficult, however, to fully satisfy both the recently increasing recording density and durability requirements. For example, an attempt to increase recording density by smoothing the surface of the recording medium as much as possible results in an increase of contact area with a magnetic head, which will cause sticking of the medium to the magnetic head. It tends to follow that the magnetic layer is peeled, causing dropouts. Application of the above-mentioned proposal is still insufficient for solving this problem.
Conventional techniques relating to the hardness of layers constituting a magnetic recording medium include the one disclosed in Japanese Patent Laid-Open No. 5-298658. Aiming at improving the contact with a magnetic head thereby to minimize the spacing loss, the publication specifies that the Vickers hardness of the uppermost magnetic layer is not lower than 40 and lower than 200 and is higher than that of the lower layer by 5 or more. However, because attention is paid only to the hardness of the layers, the magnetic layer is liable to peel due to the above-described sticking to a magnetic head. Further, reduction in error rate is insufficient.